Generally, a vehicle parking brake is operated so as to actuate same by a brake lever which is provided separately from a gear-shifting change lever. Contrary to this, there is disclosed in U.S. Pat. No. 4,713,983 an art which uses a gear-shifting change lever for operating a parking brake.
The parking brake disclosed in this U.S. Patent is constructed by using a speed change transmission. That is, in a tractor having a key-shift transmission in which a series of speed change gears rotatably mounted on a speed change shaft are coupled one at a time to the change shaft using shift keys which are slidably disposed within elongated grooves in the outer surface of change shaft, recesses into which gear-engaging lugs on the free ends of shift keys may project are formed in an internal journal wall of transmission casing through which the change shaft extends. When the tractor is to be parked, shift keys are slidingly displaced using a gear-shifting change lever to a position where the gear-engaging lugs project into the recesses. By this, the change shaft is locked non-rotatably through shift keys so that an unexpected start of the tractor is prevented.
The parking brake and the actuating mechanism for it disclosed in the U.S. Patent are very simple in structure because the are provided by using a gear-shift transmission. On the other hand, a shift key employed in a key-shift transmission is made of an elongated narrow plate having a small thickness so that, when it is used for locking a vehicle so as to prevent it from starting, a deformation of the key may easily be caused particularly at its gear-engaging lug due to force, which is applied when the vehicle is parked at a slope, and due to shock which is caused when the gear-engaging lug of shift key projects, with accompanying some rotation of change shaft, into a recess formed in a stationary wall. Such deformation of the shift key will prevent a smooth gear-shift operation.
Further, this prior art can be applied only to a vehicle having a key-shift transmission and cannot be applied to a vehicle having a conventional speed change transmission in which movable shifting gears or clutch members are employed for speed change purpose.
As one of the typical gear-shifting mechanisms employed in tractors and the like, there is well-known, as shown, for example, in JP, Y2 No. 58-28251 and JP, U No. 54-95676, a mechanism comprising a horizontal control shaft which is operated by a change lever selectively to rotate and to slide. The control shaft carries one or more shifter pins each of which is engaged by a rotational or sliding movement of the control shaft selectively with one of gear-shifting forks and then will cause a sliding displacement of the fork when a sliding or rotational movement is given to the control shaft.
A primary object of the present invention is to provide a novel actuating mechanism for vehicle parking brakes which is employed in a vehicle comprising a gear-shifting mechanism having the well-known structure set forth above and in which a rotatable and slidable control shaft operated by a change lever is used also as a control member for a parking brake which is provided separately from a gear-shifting transmission.